Enhanced energy density in P(VDF-HFP) nanocomposites with gradient dielectric fillers and interfacial polarization

Abstract

Dielectric capacitors are of urgently demand in modern micro-electric industry. The surface modified inorganic filler introduced to polymer matrix represents a promising avenue for the dielectric material's enhancement of energy storage density. To ease the electric field concentration of the composite induced by permittivity difference between ceramic fillers and polymer matrix, the specific dielectric fillers of TiO2 nanowires modified BT particles were synthesized in this study. Gradient dielectric composite consisting of poly(vinylidene fluoride-co-hexafluoropylene) [P(VDF-HFP)] matrix (εr∼10), TiO2 shell (εr∼40), and BaTiO3 (BT) core (εr∼1000) were focused to investigate the electric field contribution and interface polarization. The results revealed that the permittivity of the composites increased as a result of large interfacial polarization induced by the large specific surface area of the nanowires as compared to the composite with randomly mixed TiO2/BT fillers. The breakdown strength of the composite was slightly improved with 20 vol% fillers, attributed to the fact that the electric field intensification was weakened by the BT@TiO2/Dop gradient dielectric fillers. The composite could endure up to 106 times of field cycling at the applied cycling field and the leakage current density was rather low. The composites with 20 vol% fillers exhibited a discharged energy density of 2.8 J/cm3 at a low electric field, which was much higher than that of the neat P(VDF-HFP). The findings of this research introduced a new inorganic particle with large specific surface area and gradient dielectric permittivity as filler in composite for energy storage application.